The movie plays in the pre-empire period, when China was divided into seven kingdoms. One kingdom, Qin, was way more powerful than the others and was on a steady campaign to conquer all of China. Many assassins tried to kill the king of Qin, and the movie is about one such attempt.
The story is a framestory, wherein Nameless (played by Jet Li), who claims to have killed three assassins who were after the king of Qin, converses with said king. The scenario is pretty clever, everything is told from three different perspectives: what Nameless tells the King, what the King thinks really happened, and what did actually happen.
Colors play a major part in the movie: each 'frame' in the story has its own color: actors wear robes in that color and scenery, sets and props are in that color too.
Speaking of sets and props: there are virtually none. There is very little of the lush every-day details we saw in Crouching Tiger, Hidden Dragon. This sparsity helps maintain focus on the plot and the emotions of the characters and adds a fairy-tale, mythical atmosphere to the whole movie.
And yes, there are really kick-ass fight-scenes, but the movie is not about the fighting. Somehow that really appeals to me: there's eye-candy, but that only serves to show the plot and the emotions of the characters, they are not an end in themselves.
I enjoyed this movie immensely. If you have the opportunity to see it, do so. It has very impressive directing, clever plot and excellent fighting scenes.